This application is related to U.S. Pat. No. 4,380,413 issued Apr. 19, 1983. The present invention is directed to a roofing insulation fastener assembly.
The fastening of compressible insulations to metal or concrete roof decks has required new fastening techniques, one of which is depicted in the abovenoted. With some washer configurations, a problem can arise in seating the fastener. Typically, power driven screwdrivers are used to install these fastener assemblies. Many of these screwdrivers have clutches or other drive engaging means which rely on axial displacement of the fastener head to disengage the drive. If the washer has a planar configuration, there is little movement of the head during seating. This can result in the assembly being left loose. If the clutch is adjusted for deeper drive, an over-drive situation can develop in which the insulation is compressed beyond its elastic limit.
The present invention provides a solution to this problem. A crushable region of the washer adjacent the fastener receiving aperture insures that a proper preloading of the joint occurs prior to drive disengagement. This provides a larger margin for error in adjustment of the clutch settings and reduces the chances of underdriving and overdriving.
Other features, characteristics and advantages of the present invention will become apparent after a reading of the following specification taken in conjunction with the appended drawings.